var itcast = {
	tap: function (dom, callback) {
		if (!dom || typeof dom != 'object') {
			return;
		}
		var startX, startY, startTime;
		dom.addEventListener('touchstart', function (e) {
			// 判断是否是一根手指
			if (e.targetTouches.length > 1) {
				return;
			}
			startX = e.targetTouches[0].clientX;
			startY = e.targetTouches[0].clientY;
			startTime = Date.now();
		});
		dom.addEventListener('touchend', function (e) {
			// 判断离开时是否是一根手指
			if (e.changedTouches.length > 1) {
				return;
			}
			if (Date.now() - startTime > 150) {
				return;
			}
			var endX = e.changedTouches[0].clientX;
			var endY = e.changedTouches[0].clientY;
			if (Math.abs(endX - startX) < 6 && Math.abs(endY - startY) < 6) {
				console.log('是单击事件');
				callback && callback(e);
			}
		});
	}
}